Medtronic Guardian 3: “Do Not Calibrate. Sensor Updating…” Error

Medtronic 670G Insulin Pump with "Do not calibrate. Sensor Updating" Message
Disclaimer:

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Living with diabetes has taught me a lot of life lessons. One of them is that most things we can’t control.

There is some irony in this post, as I recently wrote a blog post about how I like to start my Guardian CGM sensor on Sunday. Well, my sensor failed early and I had to start a new one on Saturday this week. The Guardian 3 CGM sensors are supposed to last 7 days but technology is imperfect and sometimes they fail early. This is actually the first time I’ve experienced this in the 8 months I’ve been using the Medtronic 670G Insulin Pump system, so I wouldn’t say that this is a common issue, but certainly something you’re likely to come across at some point.

What does “Sensor Updating” mean?

According to the Medtronic Minimed Insulin Pump 670G Auto mode FAQ webpage, this sensor updating alert means that “Your pump is performing checks to see if sensor values are reliable,” and you should follow your pump’s instructions.

If you participate in diabetes discussion forums or have spent much time reading on the internet, then you’ve probably come across people talking about the error message “Do not calibrate. Sensor Updating. ” From the anecdotes that I’ve read, it seems likely that the sensor will fail. If it fails, you will see a “Change sensor” message. However, the “Sensor updating” alert can stay on for 3 hours and does not mean failure will definitely happen.

You can wait to see if the sensor starts working again, or you can change the sensor as a precaution.

Get a replacement senor

If you want to get a replacement sensor from Medtronic due to the “Sensor updating” alert, it’s probably best to wait the 3 hours to see if the sensor fails, since “Did the sensor updating message last longer than 3 hours?” is one of the questions on their sensor replacement form.

There is an online sensor replacement form available, but it didn’t work when I tried it. There were errors in the developer console and it was impossible to complete. If the online form doesn’t work for you, then try calling Medtronic support. Links to form based on country: USA Customers. Canada customers.

I have called Medtronic in the past and they are very good about sending out a replacement sensor. I once had a sensor that didn’t work at all (starting from day 1, I was unable to calibrate and got the change sensor message), and they sent a replacement sensor. It’s a good idea to save the piece of paper that has the sensor lot number on it, so that you can report the lot number when it fails. However, that is not required to get a replacement.

When the sensor is updating, the sensor does not display a glucose number. The insulin pump, if in auto mode, may switch to Safe Basal mode.

Be prepared for sensor failure

In my experience, sensor failure before 7 days is uncommon. However, it’s definitely a possibility. For me, having a sensor fail unexpectedly can be a major disruption, as I use auto mode. Without a sensor, the pump will switch into manual mode. Since there is no sensor reading, manual mode will continue to give the programmed basal rate, and the pump doesn’t know if the blood glucose is dropping too low.

I personally stay prepared for sensor failure by always carrying a glucose meter with me. That way, I can test my blood glucose and adjust my basal rate up or down depending on if I’m trending low or high. This requires more work on my part, and makes me somewhat anxious. But, at least it’s a back up plan. It’s better than no plan.

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